1 Field of the Invention
The present invention relates to a tapping pipe for a melt vessel such as a converter or an electric arc furnace. A tapping pipe has flow cross-sections, or cross-sectional flow areas, that, at the level of a discharge zone of the tapping pipe, are less than at levels closer to the inside of the converter or electric arc furnace.
2 State of the Prior Art
The type of tapping pipe mentioned above is described in EP 0 057 946 B1. In this tapping pipe, the flow cross-sections of the tapping pipe taper in steps from a feed zone closer to the inside of the converter toward the discharge zone of the tapping pipe. In this manner, the tapping channel of the tapping pipe is adjusted to the flow conditions of the tapping stream.
When a tapping pipe wears, the flow resistance of the tapping pipe decreases. Consequently, the tapping period, and thus the period of time in which the converter empties, starting from its maximum bath level down to its minimum bath level, changes accordingly. This is a disadvantage, because the tapping time affects the temperature of the melt in the next, downstream, vessel. Thus a prolonged tapping period will result in lower melting temperatures in the following vessel than with shorter tapping periods. To avoid the resulting metallurgical irregularities, the melt then has to be reheated. This requires a considerable amount of energy.